Dental casting



Nov. 8, 1949 H. FREEDMAN 7 2,487,048

DENTAL CASTING Filed June 12, 1945 INVENTOR. Hyman Freedman Patented Nov. 8, 1949 UNITED STATES PATENT OFFICE 3 Claims. 1

This invention relates to the art of making castings of metals generally and, more particularly, to the art of casting dental fillings.

One object of the invention is the provision of a method and means for making such castings whereby a considerable amount of labor such as cutting and grinding is saved in the production of such castings.

Another object of the invention is to provide such method and means which will prevent the formation of unnecessary projections at the top of the casting thus saving a considerable amount of precious metal.

Other objects and advantages will appear as the nature of the improvements is better understood, therinvention consisting substantially in the novel arrangements and co-relation of parts herein fully described and illustrated in the accompanying drawings, wherein similar reference characters are used to describe corresponding parts throughout the several views, and then finally pointed out and defined in the appended claims.

The disclosure made the basis of exemplifying the present invention suggests a practical embodiment thereof, but the invention is not to be restricted to the exact details of this disclosure, and the latter therefore, is to be understood from an illustrative, rather than a restrictive standpoint.

In accordance with a preferred form of the present invention, the device comprises a hollow tubular sprue which may have tapering sides at one end thereof, the sprue being preferably provided, with a pin or similar article for insertion into a wax pattern for removal of same from the dental cavity, the tapering sides of the sprue acting to form a frangible area in the finished casting'in a'manner which will be hereafter de-' scribed.

Figure 1 is a front view in elevation, at an enlarged scale of the sprue and pin;

Figure 2 is a longitudinal section showing the pin as being inserted into a wax filled cavity;

Figure 3 is a sectional view through a mold showing same as being provided with an opening havin tapering sides left by the sprue;

Figure 4 is a side view in elevation of a modified form of the sprue;

Figure 5 is a view looking from the right of Figure 4;

Figure 6 is a sectional view through a mold formed with the use of the modified sprue;

Figure 7 is a sectional View taken on line l--l Figure 6, and

Figure 8 is a side view of a dental filling showing a strip of mica or other similar material left in the mold by the sprue and imbedded in the casting so as to provide a frangible area for the easy removal of the cast sprue or projection at the top of the casting.

In the waxing up method for making wax patterns now commonly employed, a heated pin or other similar holder is inserted into the wax pattern. During said operation the melted wax tends to flow onto the holder and form therewith an irregular fillet-like juncture. As a result of this piling up, the same irregular formation will be transferred to the mold and finally to the casting, thus necessitating a great amount of labor in the removal of same and also causing a Waste of the precious metal.

It is to obviate these undesirable features that the present improved method and means of casting dental and other fillings has been perfected.

Referring now to the drawings in detail and, more particularly, to Figures 1, 2 and 3, the numeral I0 indicates a preferably hollow tubular sprue provided with tapering side portions II at the bottom thereof. The bottom of the sprue at the sides Il may be provided with short notches, cuts or slots 12. The sprue may be provided with short pins or projections l2a. A pin l3 having a shank I4 and a head I5 is adapted to pass through the inner bore l6 of the sprue. The contour of the shank l4 may be of somewhat irregular and corrugated formation and end in a somewhat bent point H.

In practice the sprue I0 is placed in the best possible position over the wax pattern l8 shown in dot and dash lines, Figure 2, only lightly engaging same. At that time the wax will enter the slots l2. The operator while holding the sprue between the thumb and second finger, applies pressure to the head l5 by the forefinger causing the point I! to be pushed into the wax pattern.

The somewhat hooked formation of the point I! will facilitate the ready removal of the wax pattern from the cavity of the tooth l9 being operated upon without appreciable alteration of the surface of the pattern.

After the removal of the wax pattern from the cavity, a mold 20 may be formed in the usual manner by pourin investment material about the pattern.

The sprue l0 and pin l3 may be pulled out of the mold, and the wax pattern heated and evaporated through the opening 2| at the top of the 53 mold formed throughout its greater length by the tapering sides I l of the sprue.

When casting the filling or other object, the molten metal is poured into the mold through the opening 2| and after filling the mold cavity 22, the rising material will produce a cast sprue in the opening with a substantially reduced portion corresponding to the section 24 which at its juncture with the top of the filling forms a frangible area due to which the cast sprue 23 may be easily broken oil directly at the casting after the removal of the casting from the mold.

It will be seen that due to the piercing technique herein employed, no unsightly unwanted fillet formation is possible about the .juncture of the casting and cast sprue 23. This technique virtually preserves the originalslhaipeof the wax pattern at the juncture of pattern and cast sprue. It will readily be understood that a fillet formation at the base of the sprue 23 makes it impossible to break same off at that point with the consequent result that a great deal of time and labor is spent in sawing same oil and then grinding the surface smooth, as well as guessing at the 'correctform of the surface. Likewise a considerable amount of metal is saved by the omission :of "the said sawing and grinding operations.

In the modified form of the invention shown in Figures 4, 5, 6, 7 and '8, there is provided a sprue 25 having a spring clip '26 adapted to hold a strip of mica 21 or other similarmaterial. The said mica strip may be bent at right angles, the vertical wall 28 thereof being held between the outer surface of the sprue and the clip 25 while the horizontal wall 29 is held laterally between a pair of pins or prongs 38 at the bottom of the sprue.

In this modified form of the invention the prongs 30 are inserted into the Wax pattern which pattern is then extracted from the tooth cavity and the investment material is poured to form the mold 20a. When the mold is thus formed the'mica-stripbecomes imbedded along its vertical edges 3! in the investment material. The sprue is then withdrawn from the mold disengaging itself from the mica strip'which'remain's imbedded in the orifice 2m. Then the wax pattern is evaporated from the mold. The flap 29 of the mica strip 2! forms a hinge with the vertical portion 28 and extends between the mold cavity 32 and the passage 2la directly above the mold cavity.

When casting the filling 33 the molten metal is poured through the passage 21a and will push downwardly the flap '29 'of the mica strip 2'1. The level of the molten metal in the mold cavity 32 :will rise gradually and will move the fiap 29 back to its horizontal position. After filling the mold cavity 32, the molten metal will fill the opening or orifice 21a and will form a cast sprue 34 in the bottom of which the flap 29 will be imbedded in such a manner as to provide a very weak area 35 at which area the cast sprue 34 may be broken off without any great exertion.

From the foregoing it will be seen that in the first form of the invention a progressively reduced area is provided at the juncture of the casting and its sprue cast by means of tapering sides or progressively diminishing diameters of the wax pattern-holding sprue, with the weakest breaking point directly at the surface of the casting; in the modified form of the invention the mica strip acts to form the weak area. Thus, in both instances, there is provided :a weakened or frangible area directly at the surface of the casting at which the cast sprue may be quickly, easily and effectively removed.

While the invention has been shown and described as relating to dental fillings, it is to be understood that the invention may as readily be utilized in the production of a great variety of other castings without departing from the scope of the appended claims.

What is claimed is:

1. For use in combination with a mold for casting dental fillings or other objects, a hollow sprue having opposed tapering sides near the bottom thereof and roundsurfac'es joining saidtap'ering sides, and a pinp assing longitudinally through the sprue and adapted to be inserted into a wax pattern, the sprue having notches at the bottom thereof for the admission of pattern material, and further having two diametrically disposed pins for holding the pattern materiaL'the taper ing sides being adapted -to form a restricted area in the mold at the juncture 'of the cavity in the mold formed by the pattern and'th'e opening by the sprue.

2. For use in forming a'mold "for casting 'various articles, a casting adjunct comprising a pattern-holding hollow sprue tapering at one end to a thin, flat edge, 'said edge having pointed projec'tions at opposite ends of said edge.

3. For use in forming a mold for casting various articles, a casting adjunct comprising apatternholding hollow sprue, the pattern-engaging end being tapered .at least on one side and having at least two projections depending from the extremity of the pattern-engaging end.

HYMAN FREEDMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Bard Mar. 9, 1920 

